High velocity liquid jet



United States Patent [72] Inventor Norman C. Franz 3311 Dale View Drive, Ann Arbor, Michigan 48103 [21] Appl. No. 733,495

[22] Filed May 31, 1968 [451 Patented Aug. 18, 1970 [54] HIGH VELOCITY LIQUID JET 16 Claims, 9 Drawing Figs.

3,136,649 6/1964 Keahey,Jr 3,212,378 10/1965 Rice Primary Examiner- Frank T. Yost ABSTRACT: A method for improving the cohesiveness ofa high velocity liquid jet by dissolving a long chain polymer in the working liquid which is pressurized and ejected through a discharge nozzle as the liquid jet is described. The improved cohesiveness of the liquid jet particularly increases its depth penetration effectiveness into a work surface and reduces wetting when severing absorptive work materials. Particularly described is the use of a water soluble long chain polymer dissolved in water. The high velocity liquid jet is particularly useful for cutting, separating, piercing or otherwise penetrating various work surfaces to obtain a desired final form or configuration.

Patented Aug. 18,

Sheet of 2 awe. 4"

ATTORNEYS HIGH VELOCITY LIQUID JET SUMMARY OF THE INVENTION The present invention relates to the method for producing an improved high velocity liquid jet. More particularly the present invention relates to a method for producing a high velocity liquid jet which has improved cohesiveness particularly reflected in increased depth penetration effectiveness.

PRIOR ART The use of high velocity liquid jets for penetrating various I work surfaces is well known to the prior art. Representative of such prior art are United States Patent Numbers 2,985,050 and 3,212,378 wherein the method and apparatus is described in detail. In general the method and apparatus involves pressurizing a working liquid which is ejected through a discharge nozzle in the form of the high velocity liquid jet using the techniques described in these patents.

The problem with these and other prior art methods is that the high velocity jet produced tends to be dispersed upon being ejected from the nozzle and the greater the pressures upon the working liquid, the greater the dispersion which is produced. This dispersion ofthe high velocity jet reflects itself in poor penetration effectiveness of the jet, tends to produce irregular penetration along the prescribed path ofpenetration, and often results in unwanted wetting of the work surface. For these reasons the high velocity liquid jets have not found wide useage where depth of penetration, regularity of cut or absence of wetting are important factors.

OBJECTS It is therefore an object of the present invention to impart properties to the working liquid, particularly water, which improves the cohesiveness or energy density ofthe high velocity liquid jet and minimizes dispersion, disintegration or breakup ofthe liquid jet leaving the nozzle. It is further an object ofthe present invention to minimize the temperature of such jets produced at a given working fluid pressure. Further still it is an object of the present invention to easily and economically achieve the improved cohesiveness of the high velocity liquid jet without impairing the flow rate or velocity level and to allow the use of smaller nozzle cross sections and/or lower pressures on the working liquid than is presently possible in the art. These and other objects will become increasingly apparent to those skilled in the art by reference to the following description and the drawings.

IN THE DRAWINGS FIGURE l is a schematic view illustrating a nozzle in crosssection with a cylindrical hole and the associated pressurizing system for the working liquid.

FIGURE 2 is a schematic enlarged view ofthe nozzle shown in FIGURE l illustrating the very turbulent flow of a prior art working liquid in the nozzle hole and the dispersion of the jet upon exit from the nozzle.

FIGURE 3 is a schematic enlarged view ofthe nozzle shown in FIGURE l illustrating the non turbulent or more nearly laminar flow of the working liquid combined with the long chain polymer in the nozzle and the cohesiveness of the liquid jet upon exit from the nozzle.

FIGURE 4 is a cross-sectional view ofthe liquidjet shown in FIGURE 3 illustrating the cohesive liquid jet.

FIGURE 5 is a schematic cross-sectional view of the dispersed liquid jet shown in FIGURE 2 illustrating the dispersion.

FIGURES 6, 8, and 9 are graphs illustrating depth of cut versus long chain polymer concentration in the working fluid or the viscosity of the combination and FIGURE 7 is a graph of concentration versus viscosity for a particular polymer at the low shear rates of a viscosimeter.

GENERAL DESCRIPTION The present invention relates to a method for increasing the cohesiveness ofa fine high velocity jet produced by pressurizing a working liquid which is ejected through a discharge nozzle in the form of the high velocity liquid jet which comprises:

(a) providing a long chain polymer dissolved in the working liquid in an amount such that the combination exhibits a higher viscosity (usually substantially higher) at low shear rates than the working liquid alone; and

(b) pressurizing and ejecting the combination through the nozzle in the form of a relatively more cohesive high velocity liquid jet when compared to the working liquid alone. The use of the long chain polymer particularly increases the penetration effectiveness of the liquid jet into a work surface, although the liquid jet can be used for other purposes such as jet fuel injection, surface cleaning and the like.

The unexpected feature of the present invention is that the long chain polymer dissolved in the working liquid exhibits a low apparent viscosity at the very high shear rates encountered when the combination is discharged through the nozzle. At low shear rates which are encountered with conventional viscosimeters the combination has a substantially higher viscosity than the working liquid alone. It would be expected that the substantially higher viscosity ofthe working fluid with the dissolved long chain polymer would seriously decrease or stop the flow rate and velocity of the liquid jet since viscosity normally does not greatly decrease with increasing pressure on a fluid.

Referring to FIGURES l to 5, a high velocity jet is illustrated. Conventional jet apparatus is illustrated in FIGURE 1 wherein a nozzle 10 comprising a fine hole 11 usually tubular (between about 0.003 and 0.500 inch long or 3 to 30 diameters) and circular in cross-section (between about 0.001 and 0.1 inch in diameter) in a housing 12 with a rounded entry 14 is shown. The working fluid 17 enters the hole 11 to produce the jet 18. Thread I3 or other connecting means are provided in the housing 12 ofthe nozzle 10 entry 14 connected to a high pressure line 15 connected to a pressurizing system 16 for the working fluid I7. FIGURE 2 shows the turbulent working fluid 19 in the hole in the nozzle 10 when no long chain polymer is provided in the working fluid l7 and in FIGURES 2 and 5 the dispersion of the jet 20 produced. FIGURE 3 shows the non turbulent working fluid 21 in the hole 11 in the nozzle I0 and in FIGURES 3 and 4 the cohesive jet 22 produced upon exit from nozzle I0. The high shear forces upon the moving working liquid at the interface between the working liquid 21 unexpectedly act upon the linear polymer at the interface to substantially reduce the coefficient of friction at the interface and the polymer reduces the dispersion of the jet 22 produced. A cohesive jet 22, is produced without substantially reduced velocity.

Long chain polymers, including natural or synthetic polymers, are well known in the prior art and are suitable for use in the present invention providing they can be dissolved in the working liquid such as by direct dissolution in the working fluid with or without the application of heat or by the use of solvents for the linear polymer which are miscible with the working liquid. Long chain polymers which are usually suitable are those where the molecular chain is essentially linear and not substantially cross linked with adjacent molecular chains although there can be branching within individual chains. In general. the preferred long chain polymers have an average molecular weight between about 10,000 and 7,000,000. Specific examples are polyalkylene oxides, particularly polyethylene oxide which is usually dispersed in a lower alkanol having I to 6 carbon atoms such as isopropanol and introduced into the working liquid usually water; alkyl substituted celluloses such as the methyl celluloses which are introduced into the heated working liquid usually water and the mixture is then cooled to bring the methyl celluloses into solution; and gelatin which is dissolved in the working liquid usually water. As will be appreciated the particular long chain polymer selected must be dissolvable in the working liquid in order to properly function for the purposes of the present invention so that the characteristics of the working liquid will determine in part the selection of the long chain polymer.

Numerous working liquids are known to the prior art, however the most economical for penetration purposes is water and this is very much preferred for this purpose of the present invention. Other fluids which have been suggested are various low viscosity non-chlorinated oils, alcohols, glycerine and various mixtures of alcohols and glycerine with water. All are characterized by having low viscosities near the viscosity of water. The linear polymer in each mixture increases the cohesiveness of the liquid jet.

In general high velocity jets are those preferably in the range between about 500 and 4000 feet per second, or more, at the exit from the nozzle and are usually traveling at a velocity at or exceeding the velocity of sound in air (1080 feet per second). In order to produce these velocities the working liquid is pressurized to between about 10,000 and 100,000 pounds per square inch, or more, and the nozzle is usually circular in cross section with a diameter of between about 0.001.

inch and 0.1 inch depending upon the particular combination of working fluid and linear polymer. The nozzles can have other cross-sectional shapes having an area between 0.000001 and 0.01 square inches although this is not preferred. It is preferred to have a rounded entry and square exit in the nozzle hole as shown in FIGURE 1.

It has been found that it is preferred to use between about 500 and 30,000 parts (particularly between 1,000 and 10,000 parts) of the long chain polymer per million parts of the working liquid. It is also preferred that the viscosity of the combination at low shear rates be between about and 1000 times greater than the viscosity of the working liquid alone. These SPECIFIC DESCRIPTION The following are examples of the operation of the method of the present invention wherein water is used as a representative working fluid.

Example I Using the equipment previously described and a 0.0075 inch in diameter, 0.075 inch long nozzle hole with a pressure on water as working fluid of 40,000 pounds per square inch, pine wood was cut with a feed rate perpendicular to the jet of 0.85 inch per second. The depth of cut in inches was measured versus the concentration of polyethylene oxide polymer (Polyox WSR-301 Union Carbide in parts per million in the water (dispersed at about twenty-five to thirty-five percent by weight in isopropanol and added to the water) at distances from the nozzle of one eighth inch We") and one and one eighth inch (1 54:) to determine the cutting effectiveness. The results are shown in the graph FIGURE 6. As can be seen from FIGURE 6, the addition of about 500 to 10,000 parts per million of the polyethylene oxide polymer substantially increases the depth of cut effectiveness of the working fluid. Within this range, the viscosity of the working fluid (low shear rates) using a Brookfield Syncro-Lectric viscosimeter was found tobe between just above 1 and 1600 centipoises as shown in FIGURE 7 and it was found that the higher working fluid and polymer combination viscosities were greatly reduced (60 to 90 percent) when the fluid from the jet was tested with the viscosimeter because of the high shear rates in the nozzle (about 10"sec"). This linear polymer had the physical characteristic of decreasing its measured viscosity with increasing low shear rates encountered with the viscosimeter.

It was found that the calculated friction coefficient for the water with the polymer was less than that for water alone at jet velocities in excess of about 452 feet per second with the 0.0075 inch diameter nozzle and that this cross over velocity point was greater for larger diameter nozzles and less for smaller diameter nozzles at equivalent pressures. At velocities below the crossover velocity point, the friction coefficients were greater than that for water alone.

The following Example II shows the results when the natural polymer gelatin is dissolved in water as the working fluid.

Example II The procedure of Example I was repeated, using gelatin as the linear polymer which was dissolved in water. The pressure on the working fluid was 20,000 and 17,000 pounds per square inch and a 0.0095 inch diameter, 0.25 inch long nozzle hole was used. A feed rate of 0.8 inch/second and a hardwood block one eighth inch the nozzle was used. The results are shown in the graph FIG. 8 wherein it can be seen that the gelatin in a concentration of between about 1000 and 30,000 parts per million significantly increases the cut depth into the hardwood.

The viscosity of the gelatin and water did not seem to decrease with increasing shear at the low shear rates encountered with the viscosimeter as did the linear polymer in Example I, however the apparent viscosity at the high shear rates in the nozzle was much less and the friction coefficient was less than the coefficient for water alone when the jet velocity was greater than about 2500 feet per second.

Gelatin was found to work well as a linear polymer; however, care must be taken to insure that it is not biodegraded before use. It was also found that higher concentrations of gelatin were necessary for the same depth of cut produced with the polyethylene oxide of Example I.

The following Example III shows the cutting result obtained with a converted natural material, methyl cellulose.

Example III surface (Douglas fir) was one eighth inch (/a") from the nozzle. The results are shown in the graph FIGURE 9 wherein the cut depth is measured versus the viscosity in centipoises of the working fluid measured with the Brookfield viscosimeter, which is directly related to the concentration of the methyl cellulose in the water. It was found that the cut depth was significantly increased (twice as great) with a viscosity greater than about 200 centipoises up to 4000 centipoises (2 percent by weight polymer in Water). At velocities in excess of about 2000 feet per second the friction coefficient was less than for the friction coefficient of water although higher than that for the polymer of Example I.

It was found the methylcellulose long chain polymers are preferred since they could easily be dissolved directly in water. They are also non-toxic and the viscosities were not substantially reduced as a result of passage through the nozzle at high shear rates thus making possible their reuse.

The procedure of Examples 1 to "I was repeated with polyacrylamide and polyethylenimine long chain polymers (Separan SAl291.1,SA1291,SA1214.5 and AP 273 Dow and Montrek PEI-1000 Dow) and these materials were useful; however, the viscosities and/or degradation make them less suitable than those of the above Examples. The friction coefficient for PEI 1000 was greater than water at a viscosity of 60 centipoises and the friction coefficient became excessive for higher viscosities 'l'he long chain polyacrylamide polymers (Polyhall 295 and 402, Stein Hall & Co.) produced good results when the polymer degradation as a result of passage through the nozzle was not excessive.

It was found that the long chain polymers increase the effective life of the nozzles and high pressure pump packings or seals. It was also found that the temperature of the jet was substantially reduced because of reduced friction in the nozzle and that as a result greater working fluid pressures could be used without vaporization of the jet leaving the nozzle. Further since the concentrations of the long chain polymers are low the method is economic. An important effect of the addition of long chain polymers was found to be the reduction of surface and internal wetting of the work.

It was also found that when finely divided solid materials were added to the working fluid for facilitating the cutting of hard materials the long chain polymer reduced the erosion of the nozzle by the solid material. Particularly useful were glass beads. in all cases the solid materials were smaller in diameter than the nozzle hole.

The foregoing description is intended to be only illustrative of the present invention and it is intended that the present in vention be limited only by the hereinafter appended claims.

lclaim:

1. The method for increasing the cohesiveness ofa fine high velocity jet produced by pressurizing a working liquid which is ejected through a discharge nozzle in the form of the high velocity liquid jet which comprises:

(a) providing a long chain polymer dissolved in the working liquid in an amount such that the combination exhibits a higher viscosity at low shear rates than the working fluid alone; and

(b) pressurizing and ejecting the combination through the nozzle in the form of a relatively more cohesive high velocity liquid jet when compared to the working liquid alone.

2. In the method for subjecting a work surface to a penetrating action wherein a working liquid is pressurized and ejected through a discharge nozzle in the form of a fine high velocity jet and then directed against the work surface the step which comprises:

providing an amount of a long chain polymer dissolved in the working liquid sufficient to increase the depth of penetration of the resulting high velocity jet into the work surface with equivalent pressures and nozzles.

3. 1n the method for subjecting a work surface to a penetrating action wherein a working liquid is pressurized and ejected through a discharge nozzle in the form of a fine high-velocity jet and then directed against the work surface the step which comprises:

providing a long chain polymer dissolved in the working liquid in an amount such that combination exhibits a substantially higher viscosity at low shear rates than the working liquid alone and sufficient to increase the depth of penetration of the resulting high velocity jet into the work surface with equivalent pressures and nozzles.

4. The method of Claim 3 wherein the working liquid is water in combination with the long chain polymer.

5. The method of Claim 3 wherein the viscosity of the combination at low shear rates is between about 10 and 1000 times greater than the working liquid alone.

6. The method of Claim 3 wherein between about 500 and 30,000 parts of long chain polymer are provided per million parts of the working liquid.

7. The method of Claim 3 wherein the working liquid is water and wherein between about 500 and 30,000 parts of long chain polymer are provided per million parts of the water.

8. The method of Claim 3 wherein the long chain polymer is dispersed in a solvent miscible with the working liquid and then combined with the working liquid.

9. The method of Claim 8 wherein the working liquid is water and the solvent is a lower alkanol and the long chain polymer is a polyalkylene oxide.

10. The method of Claim 9 wherein the polyalkylene oxide is polyethylene oxide.

11. The method of Claim 3 wherein the long chain polymer is dispersed in the working liquid by applying heat, and then coolin 12. lhe method of Claim 11 wherein the long chain polymer is gelatin.

13. The method of Claim 11 wherein the long chain polymer is methyl cellulose.

14. The method of Claim 3 wherein the average molecular weight ofthe long chain polymer is between about 10,000 and 7,000,000.

15. The method of Claim 3 wherein the velocity ofthe high velocity jet is between about 500 and 4000 feet per second.

16. The method of Claim 3 wherein the the working liquid is pressurized between about 10,000 and 100,000 pounds per square inch and wherein the nozzle is circular in cross section with a diameter between about 01001 inch and 0.1 inch. 

